Source: Watershed Crop Data Layer from the National Agricultural Statistics Service (NASS) (2013).

The Clearwater watershed covers an area of 886,632 acres. Approximately eighty percent of the land in the watershed is owned by private landholders (706,928 acres). The second largest ownership type is State, with approximately 78,320 acres (8.8%), followed by Tribal with 56,444 acres (6.4%), Private-Major with 31,388 acres (3.5%), Federal with 9,558 acres (1.1%), and Conservancy with 3,231 acres (0.4%). County lands account for the smallest percentage, with slightly more than 800 acres (0.1%). Predominate land uses / land covers are Row Crops (33%), Forest (24%), Grass/Pasture/Hay (21%), Wetlands (14%), and Residential/Commercial Development (4%). Agricultural land use in the basin accounts for approximately 54% of the overall watershed acres.

Development pressure is moderate in most areas, with occasional farms, timberland, and lakeshore being parceled out for recreation, lake or country homes. Source: Clearwater River Rapid Assessment - NRCS

Nitrogen

Vertical Tabs

Nitrogen Overview

What is Nitrogen?:

Nitrogen (N) is one of the most widely distributed elements in nature and is present virtually everywhere on the earth’s crust in one or more of its many chemical forms. Nitrate (NO3), a mobile form of N, is commonly found in ground and surface waters throughout the country. Nitrate is generally the dominant form of N where total N levels are elevated. Nitrate and other forms of N in water can be from natural sources, but when N concentrations are elevated, the sources are typically associated with human activities (Dubrovski et al., 2010). Concerns about nitrate and total N in Minnesota’s water resources have been increasing due to effects of nitrate on certain aquatic life and drinking water supplies, along with increasing N in the Mississippi River and its impact on Gulf of Mexico oxygen depletion.

Precipitation amounts have a pronounced effect on nitrate loads. During a dry year, loads may drop by 49% compared to an average year, however during a wet year, overall loads may increase by 51%.

Nitrate concentrations and loads are high throughout much of southern Minnesota, resulting largely from leaching through large parts of intensively cropped soils and into underlying tile drains and groundwater.

Cropland sources account for an estimated 89 to 95% of the nitrate load in the Minnesota, Missouri, and Cedar Rivers, and Lower Mississippi River basins.

Tile drainage pathwayIn tiled cropland, most of the rainwater that ends up in surface water (ditches, streams) flows through tile drainage. This water can be high in nitrate, but can potentially be treated before reaching ditches.

Groundwater pathwayIn cropland without tile drainage, most rainwater flows through the ground to get to surface waters. As it travels through the earth, some of the nitrate is removed, resulting in less nitrate reaching our streams and rivers. However, there are fewer options of controlling this kind of nitrate pollution once it moves below the crop roots.

Where does the nitrate go?

Groundwater nitrate can take from hours to decades to reach surface waters.

The Minnesota River adds twice as much nitrate to the Mississippi River as the combined loads from the Upper Mississippi and St. Croix Rivers.

On average, 158 million pounds of nitrate leaves Minnesota per year in the Mississippi River — 75% comes from Minnesota watersheds.

Nitrate concentrations have steadily increased in the Mississippi River since the mid-1970s.

Nitrate loads leaving Minnesota via the Mississippi River contribute to the oxygen-depleted “dead zone” in the Gulf of Mexico (currently estimated to be the size of Massachusetts). The dead zone cannot support aquatic life, affecting commercial and recreational fishing and the overall health of the Gulf.

How do we reduce the nitrate going into surface waters?

Tactics for reducing cropland nitrate going into surface waters fall into three categories:

Nitrate fertilizer efficiency has improved during the past two decades. While further refinements in fertilizer rates and application timing can be expected to reduce nitrate loads by roughly 13% statewide, additional and more costly practices will also be needed to make further reductions and meet downstream needs. Statewide reductions of more than 30% are not realistic with current practices.

To see progress, nitrate leaching reductions are needed across large parts of southern Minnesota, particularly on tile-drained fields and row crops over thin or sandy soils. Only collective incremental changes by many over broad acreages will result in significant nitrogen reductions to downstream waters.

Nitrogen's Downstream Impacts:

Nitrogen is considered a limiting nutrient in the Gulf of Mexico, the body of water where much of Minnesota’s river and stream waters ultimately discharge. When nutrients in the Mississippi River originating in 31 states reach the Gulf of Mexico, a low oxygen “dead zone” known as hypoxia develops.

Hypoxia, which means low oxygen, occurs when excess nutrients, primarily N and P, stimulate algal growth in the Mississippi River and gulf waters. The algae and associated zooplankton grow well beyond the natural capacity of predators or consumers to maintain the plankton at a more balanced level. As the short-lived plankton die and sink to deeper waters, bacteria decompose the phytoplankton carbon, consuming considerable oxygen in the process. Water oxygen levels plummet, forcing mobile creatures like fish, shrimp, and crab to move out of the area. Less mobile aquatic life become stressed and/or dies.

The freshwater Mississippi River is less dense and warmer compared to the more dense cooler saline waters of the gulf. This results in a stratification of the incoming river waters and the existing gulf waters, preventing the mixing of the oxygen-rich surface water with oxygen-poor water on the bottom. Without mixing, oxygen in the bottom water is limited and the hypoxic zone remains. Hypoxia can persist for several months until there is strong mixing of the ocean waters, which can come from a hurricane or cold fronts in the fall and winter.

Hypoxic waters have dissolved oxygen concentrations of less than about 2-3 mg/l. Fish and shrimp species normally present on the ocean floor are not found when dissolved oxygen levels reduce to less than 2 mg/l. The Gulf of Mexico hypoxic zone is the largest in the United States and the second largest in the world. The maximum areal extent of this hypoxic zone was measured at 8,500 square miles during the summer of 2002. The average size of the hypoxic zone in the northern Gulf of Mexico in recent years (between 2004 and 2008) has been about 6,500 square miles, the size of Lake Ontario.

Minnesota Nitrogen Study
The MPCA conducted a study of nitrogen in surface waters so that we can better understand the nitrogen conditions in Minnesota’s surface waters, along with the sources, pathways, trends and potential ways to reduce nitrogen in waters.

Cropland sources contribute an estimated 73 percent of the statewide N load during an average precipitation year. Cropland nitrogen is primarily delivered to surface waters through subsurface pathways of tile drainage and groundwater.

RED RIVER NITROGEN LOADING
The U.S. portion of the Red River Basin, depicted in Figure 25, originates mostly in Minnesota and North Dakota, with a small percentage also in South Dakota. After crossing the U.S./Canadian border, additional Manitoba watersheds flow into the Red River before it discharges into Lake Winnipeg.

Minnesota’s contribution to Emerson nitrogen loads
Based on unpublished data provided by Environment Manitoba (Manitoba Water Stewardship and Environment Canada, the average Red River annual TN load between 1994 and 2008 at the Canadian border in Emerson, Manitoba was 37,326,000 pounds/year (Figure 26). Nitrate concentrations are relatively low in the Red River, and only 42% of the TN is in the nitrate form, with the remainder as TKN (organic-N and ammonia+ammonium-N). Most of the Red River load in Emerson originates in the United States, with only 5.5% coming from Canadian watersheds which flow into North Dakota before joining up with the Red River in the United States. Therefore, 94.5% of the 37 million pounds of N reaching the Canadian border in the Red River is from Minnesota and the Dakotas. Of the United States contributions, SPARROW modeling results indicate that 48% of the United States load is from Minnesota, and 52% is from the Dakotas (see Chapter B4).

Therefore, if we assume 37,326,000 pounds/year of TN at Emerson, of which 94.5% is from the United States and 48% of that amount is from Minnesota, Minnesota’s N contribution to the Red River is estimated as 16,931,000 pounds/year, on average.

United States contributions to Lake Winnipeg
Environment Canada (2011) assessed TN loads from the period 1994 to 2007, including loads from such sources as atmospheric deposition directly into Lake Winnipeg. They concluded that the Red River from the United States and Canada watersheds contributed 34% of the N load to Lake Winnipeg. In an earlier report, Bourne et al. (2002) concluded that 65% of the Red River N comes from the United States. Combining these results, we can assume that approximately 22% of the N load to Lake Winnipeg comes from watersheds in Minnesota and the Dakotas, with about 11% of the Lake Winnipeg TN load from Minnesota.

SPARROW Modeling for the Clearwater River Watershed indicated average flow-weighted mean TN concentration of 2.92 mg/l. This value represents the median FWMC of all subwatershed catchments within the Clearwater River Watershed.

SPARROW model annual TN yield results by HUC8 watershed in lbs/acre/year. The basin yields represent the total load delivered to the watershed outlet or state border divided by the sum of the SPARROW (MRB3 2002) catchment area.

Statewide Nitrate Trends

Red River of the North Trend Results
Three sites on the Red River of the North were analyzed for trends in flow-adjusted nitrate concentrations. All three sites had relatively low nitrate concentrations, although the concentrations were higher at the downstream site in Perley. No trends were detected at the upper-most location at Brushvale. At Moorhead, and just downstream from Moorhead at Perley, concentrations increased prior to 1993-95, but had no significant trends after 1993 and 1995, respectively.

Tributaries of the Red River of the North
Trends were assessed for two tributaries of the Red River of the North, the Ottertail River and the Red Lake River, each with two monitoring locations. Similar to the Red River of the North at Brushvale, nitrate concentrations were very low, mostly between 0.1 and 0.15 mg/l. At these low concentrations, the Ottertail River showed a steady increasing trend since 1982. The percentage increase was greater in Fergus Falls than at the downstream site at Breckenridge (Table 14). The Red Lake River at East Grand Forks had a trend very similar to that of the Ottertail River in Breckenridge, both with gradually increasing nitrate concentrations by 35% over the entire time of analysis. Farther upstream at Fisher, no trends were detected.

Vertical Tabs

Phosphorus Overview

What is Phosphorus?:

Phosphorus is the nutrient primarily responsible for the eutrophication (nutrient enrichment of waterbodies) of Minnesota’s surface waters. Phosphorus is an essential nutrient for plants, animals and humans. It is one of the 20 most abundant elements in the solar system, and the 11th most abundant in the earth’s crust. Under natural conditions phosphorus (P) is typically scarce in water. Human activities, however, have resulted in excessive loading of phosphorus into many freshwater systems. This can cause water pollution by promoting excessive algae growth, particularly in lakes. Lakes that appear relatively clear in spring can resemble green soup in late summer due to algae blooms fueled by phosphorus. Water quality can be further impaired when bacteria consume dead algae and use up dissolved oxygen,suffocating fish and other aquatic life.

Why is Phosphorus a Concern?:

An overabundance of phosphorus—specifically usable (bioavailable) phosphorus—results in excessive algal production in Minnesota waters. Phosphorus from point sources may be more bioavailable, impacting surface water quality more than a similar amount of nonpoint source phosphorus that enters the same surface water conditions. Total phosphorus levels of 100 or more ppb categorize lakes as highly eutrophic, with high nutrient and algae levels.

In some water bodies, the concentration of phosphorus is low enough to limit the growth of algae and/or aquatic plants. In this case, scientists say phosphorus is the limiting nutrient. For example, in water bodies having total phosphorus concentrations less than 10 parts per billion (1 ppb – equal to one drop in a railroad tank car), waters will be nutrient-poor and will not support large quantities of algae and aquatic plants.

MPCA

Phosphorus Impacts:

Phosphorus contributions to Minnesota surface waters by point and nonpoint sources are known to vary, both geographically and over time, in response to annual variations in weather and climate. Nonpoint sources of phosphorus tend to comprise a larger fraction of the aggregate phosphorus load to Minnesota surface waters during relatively wet periods, while point sources become increasingly important during dry periods.

The Minnesota Pollution Control Agency is currently developing new water quality standards for River Eutrophication and Total Suspended Solids. Visit the MPCA website for more information.

Under normal water flows, roughly two- thirds of the total phosphorus load to lakes and rivers comes from nonpoint sources such as runoff from pasture and croplands, atmospheric deposition and stream bank erosion. Phosphorus loading contributed by runoff from pastures and croplands is largest source of nonpoint phosphorus on a statewide basis. Other nonpoint sources include urban runoff, non-agricultural rural runoff and seepage from individual sewage treatment systems.

Approximately 30 percent of the phosphorus load to Minnesota waters comes from point sources such as municipal and industrial wastewater treatment facilities. The magnitude of various sources of phosphorus varies greatly throughout the state due to the diverse nature of Minnesota’s watersheds.

Average annual Total Phosphorus Load (kg) near watershed outlets based on yearly averages derived from available information collected in 2007-011.

Phosphorus Modeling

Phosphorus Modeling Yields:

SPARROW modeling
The SPAtially Referenced Regressions on Watershed attributes (SPARROW) model, developed and maintained by the United States Geological Survey (USGS), was used for the Minnesota Nutrient Reduction Strategy to estimate Total Phosphorus (TP) loads, yields, and flow-weighted mean concentrations (FWMC) in Minnesota 8-digit Hydrologic Unit Code (HUC8) watersheds and major basins.

SPARROW model annual TP yield results by HUC8 watershed in lbs/acre/year. The basin yields represent the total load delivered to the watershed outlet or state border divided by the sum of the SPARROW (MRB3 2002) catchment area.

Summary of Recent Progress in Phosphorus Source Loads by Major Basin
Efforts between 2000 and present have resulted in significant progress in reducing phosphorus loads in the Mississippi River Basin, due to both agricultural BMPs and wastewater treatment plant upgrades.

Because agricultural sources contribute the bulk of the statewide nitrogen load and a substantial portion of the phosphorus load, nitrogen and phosphorus reductions from agricultural sources are key to successfully achieving the milestones. Recommended agricultural BMPs and strategy options for promoting adoption of the BMPs to address phosphorus and nitrogen are provided in the links above.

Phosphorus: Based on the SPARROW model and the source attributions developed in the Detailed Assessment of Phosphorus Sources to Minnesota Watersheds (Barr Engineering 2004), agricultural sources contribute an estimated 38 percent of the statewide phosphorus load. A large part of the remaining phosphorus load is due to stream channel erosion, much of which is indirectly affected by agricultural runoff and intensive drainage practices (Schottler et al. 2013).

Nitrogen: Based on the Nitrogen in Minnesota Surface Waters study (MPCA 2013), agriculture contributes 73 percent of the statewide nitrogen load in a typical year.

Red River Basin Decision Information Network - Tools
A core RRBDIN service to basin residents and resource managers is to provide decision support “tools” designed to disseminate important and relevant information to aid in local, state, and regional decision-making.

Hydrology Models: HEC-HMS models for tributaries within the Red River of the North basin to assist in development and analysis of future flood damage reduction projects

NTT estimates the nutrient and sediment load leaving a farm field through surface water runoff and leaching below the rooting zone and can be used to quantify the water quality benefits of different agricultural management systems and conservation practices. Designed and developed by the USDA Natural Resources Conservation Service (NRCS), USDA Agricultural Research Service (ARS), and Texas Institute for Applied Environmental Research at Tarleton State University (TiAER), NTT is intended for use by agricultural professionals or others familiar with farm procedures and conservation practices.

Ag BMP Assessment and Tracking Tool – Houston Engineering
Solutions for improving impaired waters often rely on the use of agricultural best management practices (BMPs). The goal of this project is to collect and disseminate thorough and accurate information on the use and effectiveness of agricultural BMPs in the State of Minnesota. Stakeholders can use this information to inform, mock-up and track their BMP implementation strategies.

AG BMP Database - Houston Engineering
The goal of the Ag BMP Database is to provide a comprehensive source of information on the application and effectiveness of agricultural BMPs within the State of Minnesota. The database was developed to hold information on BMPs that are commonly used in the State to address water quality impairments for: sediment, nitrogen, phosphorus, and bacteria.

Ecological Ranking of Parcels for Prioritizing Conservation Activities – NRRI
This site provides a mapping tool by which natural resource managers can visualize and interact with a high resolution map of the spatial data layers. Managers have the ability to specify the relative importance of habitat, soil erosion potential, or other components of the Environmental Benefits Index - a score which represents a summary of the above factors., and view how the ecological ranking of parcels changes under different scenarios.http://beaver.nrri.umn.edu/EcolRank/

COST ANALYSIS PLANNING TOOLS
Minnesota Watershed Nitrogen Nitrogen Reduction Planning ToolMinnesota Watershed Nitrogen Reduction Planning Tool - Nitrogen BMP Spreadsheet (Lazarus et al., 2013)
The Watershed Nitrogen Reduction Planning Tool (Excel Spreadsheet) was developed as part of the Nitrogen in Minnesota Surface Waters Study by researchers at the University of MInnesota and Minnesota Pollution Control Agency. The project purpose was to develop a framework for a watershed nitrogen planning aid that could be used to compare and optimize selection of "Best Management Practices" (BMPs) for reducing the nitrogen load from the highest contributing sources and pathways in the watershed.